This invention relates to a large-diameter sheath and more particularly to a dual valve, reinforced, large-diameter sheath and method of use.
Expandable access catheter assemblies have heretofore been provided to facilitate the placement and removal of diagnostic and therapeutic catheters through the vascular system. Such catheter assemblies included a flexible variable-diameter catheter body, a diameter control stylet and a flexible Y-hub. The flexible Y-hub incorporates an adjustable hemostasis valve and a side port in one branch and a diameter control stylet guide wire in another branch. A flexible variable diameter catheter body is secured to the flexible Y-hub and can be expanded between a collapsed position and an expanded position by the stylet guide wire. Several deficiencies have been found in such a device. For example, the adjustable hemostasis valve is incapable of accepting large catheters. The flexible variable-diameter catheter body is objectionable in that it has a tendency to reduce in diameter and hold onto large-diameter catheters when it is attempted to place the same through the catheter body. In addition, the tip of the stylet guide wire catches a large-diameter catheter which causes elongation of the catheter body and reduction in its diameter to grab and prevent further advancement of the large-diameter catheter. Further, the tip of the stylet guidewire may, in certain circumstances, snag the variable-diameter catheter during removal. Additional problems with existing art involve the lack of safety features to protect against operator induced inadvertent advancement of a stylet guide wire distally into the vascular system beyond a desire distance. There is therefore a need for a new and improved large-diameter sheath which will overcome these deficiencies.
The present invention embodies a sheath assembly for use in introducing a catheter or other medical instrument into a corporeal vessel. The sheath assembly includes an elongate sheath tube formed of a flexible material having proximal and distal extremities and having a passage extending therethrough. The distal extremity of the sheath tube may have a reinforcing structure or means for causing radial expansion of the distal extremity of the sheath tube to an expanded diameter.
The sheath assembly further includes a backflow adapter having a body with a central opening in fluid communication with the sheath tube. The backflow adapter includes a normally closed primary valve and may include a normally open secondary valve. When the primary and secondary valves are open they permit a medical instrument to be inserted into said sheath tube and when closed form a hemostatic seal about the instrument. The sheath assembly may further include a sheath introducer capable of being disposed in the passage of said sheath tube.
In one preferred embodiment, the sheath assembly may further include a dilator assembly for radially expanding the distal end of the sheath. The dilator assembly may have first and second coaxially oriented tubular members wherein the outer member dilates the sheath. The sheath assembly may also have a one-way locking mechanism that allows the inner tubular member to move towards the proximal end of the sheath, but restricts movement towards the distal end of the sheath.
The primary valve is disposed proximal the secondary valve. The primary valve has a cylindrical member formed of a flexible material having a proximal end and a distal end configured with a bore therein in fluid communication with the passage of the sheath tube. The primary valve also has a ring gear secured to one end of the cylindrical member, a rack for driving the ring gear to cause relative rotation between the ends of the cylindrical member to cause the cylindrical member to be twisted to close the bore extending through the cylindrical member, and biasing means for urging the rack into a position wherein the cylindrical member is rotated to a closed position.
The secondary valve is secured to the proximal extremity of the sheath tube, and has a cylindrical member formed of a flexible material having a proximal end and a distal end configured with a bore therein in registration with the passage of the sheath tube. The secondary valve includes rotating means for engaging the cylindrical member for causing relative rotation between the ends of the cylindrical member to cause the cylindrical member to be twisted to close the bore extending through the cylindrical member.
In general, the present invention provides a large-diameter sheath which can be utilized with large-diameter catheters and a method for using same. The invention also provides a sheath of the above character which presents a reduced diameter at its distal end to facilitate introduction of the sheath into the vessel of a patient with less trauma. In one embodiment of the invention, a reduced diameter is achieved by using a tapered sheath introducer with a reduced diameter tip that extends proximally from the distal end of the large-diameter sheath. The invention also provides a sheath of the above character with a backflow adapter which includes a tubular diaphragm that can be moved into an hourglass or iris-like configuration to create a fluid-tight barrier around any tubular device such as a large-diameter catheter passed through the backflow adapter and the tubular diaphragm. The invention also provides a sheath of the above character in which the backflow adapter can be readily controlled.